1. Field of the Invention
This invention relates broadly to tools for use in the hydrocarbon industry. More particularly, this invention relates to a downhole imaging tool utilizing an X-ray generator.
2. State of the Art
The use of radiation in the evaluation of geological formations is a well-established art. For example, a natural gamma ray logging tool has been used to detect the presence of naturally radioactive thorium, uranium and potassium in the formation in order to identify the lithology of the formation. Other logging tools utilizing radioactive sources such as 137Cs have been used to make formation density measurements. While effective, logging tools utilizing radioactive sources have the downside that they are subject, to extensive federal and/or state regulation involving their storage, transport, use, training, handling, monitoring, etc. If the gamma-ray source could be replaced by an X-ray source, then the radiation could be turned off when not in use, and transportation regulations applicable to radioactive materials would not apply.
Because X-ray tools are perceived as replacement for tools using radioactive sources, X-ray tools for downhole imaging of a formation or a wellbore have been the source of proposals and speculation for some time. An X-ray generator for such a tool is disclosed in co-owned U.S. Pat. No. 5,680,431 to Pietras, III et al. A block diagram of one such tool with a side-by-side X-ray source and detector is disclosed in US Publication No. 2007/0041501 to Ramstad which provides concept but no details of a workable embodiment. Despite the proposals and speculation, no commercial X-ray downhole imaging tool is available in the art because of the considerable obstacles posed by generating downhole suitable X-rays and by providing suitable downhole X-ray detectors capable of generating useful information.